Agency to Invest in Treating Water for Chromium-6

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(Photo credit: Jay Calderon/The Desert Sun)

Article courtesy of  Ian James | January 25, 2015 | The Desert Sun | Shared as educational material

The Coachella Valley Water District is about to embark on its costliest infrastructure project ever, designing water treatment plants to remove a potentially hazardous heavy metal from the water supply in places from Rancho Mirage to Thermal.

The CVWD board on Tuesday will consider spending $15.5 million to hire a consulting firm to design treatment plants that would remove hexavalent chromium, or chromium-6, from the groundwater pumped from 19 wells. The water agency has estimated the total cost of building those treatment plants could be on the order of $100 million, and that would be the first of two phases in a project that will likely lead to significantly higher water rates.

The water district, like many others across the state, is taking steps to comply with a new safe drinking water limit for chromium-6 set by the California Department of Public Health. In a portion of the aquifer beneath the Coachella Valley, the groundwater has levels of chromium-6 that exceed the new state standard.

The first phase will involve building about 15 ion-exchange treatment plants in places including Rancho Mirage, Thousand Palms, Palm Desert, Thermal, La Quinta and near Desert Hot Springs, said Steve Bigley, the water district’s director of environmental services.

The water agency has determined that the water from 37 of its 96 wells will likely require treatment. The first phase would take care of about half the wells with chromium-6 levels above the state limit.

“It would be a good start, and there’s still the other half that is a more complicated assessment because it would involve looking at other options using surface water and groundwater,” Bigley said. Those other options could including building facilities to treat water from the Colorado River for drinking, or including using that imported water to recharge the aquifer and lower the chromium-6 levels through dilution.

The dangers of chromium-6 were highlighted in the 1990s by a court case launched by then-legal clerk Erin Brockovich against Pacific Gas & Electric Company, claiming groundwater contamination in the Mojave Desert town of Hinkley. After the case became widely known through the 2000 film “Erin Brockovich,” the state Legislature in 2001 passed a law instructing public health agencies to develop a drinking water standard for hexavalent chromium.

In many areas of the country, chromium-6 has been released into the environment as a pollutant from sources such as chemical plants, leather tanneries and cooling towers. In the Coachella Valley, though, water agencies say chromium-6 occurs naturally, dissolving from rocks into the groundwater.

The new drinking water limit of 10 parts per billion took effect in July. The state’s effort to set a drinking water standard for the carcinogen generated debate between environmental groups that argued for a strict limit and water agencies that warned of high costs and questioned the science behind the proposal.

Bigley said it’s too early to say how much of an impact the project will have on water rates. But the agency has informed customers at workshops that they could see their bills rise by $30 a month or more. The Coachella Valley has long had some of the lowest water rates in the state. When CVWD eventually proposes a rate hike, the increase would likely take effect incrementally over several years.

To design the treatment plants, the water district is proposing to hire the New York-based firm Hazen and Sawyer Environmental Engineers & Scientists, which already prepared a related study at a cost of about $900,000. That company was originally selected through a competitive process for the study, but this time, CVWD managers are recommending the board hire the company without going through an open solicitation of proposals in order to expedite the process.

“We’re just trying to move ahead as quickly as possible,” Bigley said.

The CVWD board on Tuesday will consider whether to approve a total of $17.2 million for the design of treatment plants and other related work. In addition to the $15.5 million for Hazen and Sawyer, that includes $100,000 to cover CVWD’s engineering costs and $1.6 million in contingency funds to cover any unexpected expenses or cost overruns.

Other water agencies that have large numbers of wells with levels of chromium-6 above the limit include Indio Water Authority and Coachella Water Authority. Representatives of those city agencies, as well as the private Myoma Dunes Mutual Water Company, have met with CVWD officials to discuss how they could work together to reduce the costs of treating water.

Ian James can be reached by email at ian.james@desertsun.com and on Twitter: @TDSIanJames.

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